The spying technology, called “Legal Intercept,” would allow currently existing products to be modified to “cause the communication to be established via a path that includes a recording agent,” according to the filing with the U.S. Patent and Trademark Office. Once a connection is established, the agent is able to “silently record” a conversation.

The filing specifically calls out the ability to record any kind of voice-over-Internet-protocol (VoIP) communications. “VoIP may include audio messages transmitted via gaming systems, instant messaging protocols that transmit audio, Skype and Skype-like applications, meeting software, video conferencing software, and the like,” Microsoft said in the filing.

Microsoft filed for the patent in Dec. 2009, long before it acquired Skype. It’s possible Microsoft simply has this on the books so it could profit from licensing the technology to law enforcement agencies. Alternately, Skype’s purchase could have been a strategic buy to help test and deploy this new technology.